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Aim: This study aimed to compile data on the effectiveness of music therapy for patients undergoing cardiothoracic surgery. Background: After cardiac and thoracic surgery, patients often experience physiological and psychological complications, such as anxiety, pain, stress, depression and changes in vital signs, which have a great impact on prognosis. Methods: A systematic search of six databases was performed to identify randomized controlled trials investigating music therapy and cardiothoracic surgery. The data were extracted from the qualified research, the data without heterogeneity were analysed by random-effects model (REM) meta-analysis, and the data with heterogeneity were analysed by fixed-effects model (FEM) meta-analysis. We evaluated anxiety, pain, duration of mechanical ventilation, hospital length of stay, stress hormones, opioid consumption, and vital signs, including heart rate (HR), respiratory rate (RR), oxygen saturation (SpO2), diastolic blood pressure (DBP), and systolic blood pressure (SBP) after cardiothoracic surgery. The meta-analysis and sensitivity analysis were performed with RevMan 5.4 and Stata 14 software, and trial sequential analysis was conducted using TSA 0.9.5.10 Beta software. This study was conducted in accordance with the PRISMA guidelines and was registered with PROSPERO. Results: The study included 24 randomized controlled trials with a total of 1576 patients. Our analysis showed that music therapy can significantly reduce the anxiety scores (SMD= -0.74, 95% CI [-0.96, -0.53], p < 0.01) and pain scores (SMD= -1.21, 95% CI [-1.78, -0.65], p < 0.01) of patients after cardiothoracic surgery. Compared with the control group, music therapy dramatically raised postoperative SpO2 (SMD = 0.75, 95% CI [0.11, 1.39], p = 0.02). In addition, the experimental group had significant statistical significance in reducing HR, SBP and opioid consumption. However, there was no significant difference in respiratory rate, stress hormones, diastolic blood pressure, length of hospital stay, or the duration of mechanical ventilation between the two groups. Conclusions: Music therapy can significantly reduce anxiety, pain, HR, SBP, and postoperative opioid use and even improve SpO2 in patients who undergo cardiothoracic surgery. Music therapy has a positive effect on patients after cardiothoracic surgery with few side effects, so it is promising for use in clinics. Trial registration: RROSPERO (registration number: CRD42023424602). [ABSTRACT FROM AUTHOR]

Heart rate variability (HRV) is a useful method to study the autonomic nervous system (ANS) status. As measuring devices have developed and become smaller, many researchers have become interested in the possibilities to implement the method for diving medicine research. The aim of this study was to review human ANS responses in cold water diving (water temperature <5°C), and to comprise the current knowledge of HRV studies in diving and hyperbaric exposure into one review article. A literature search was conducted on 5 Decemberth 2022, with the search terms "HRV" or "heart rate variability" and "diving" or "diver" or "divers", with search functions of the data bases PubMed and Ovid Medline. Peer reviewed original articles, review articles and case reports were accepted to this review. Twenty-six articles met the pre-defined criteria and were included in this review. Studies from very cold water conditions were rare, but suggested that cold strengthens the ANS responses of diving – especially parasympathetic nervous system (PNS) activity due to the trigeminocardiac reflex and baroreceptor and cardiac stretch receptor activity, caused cold and pressure-induced centralisation of the blood. Overall, studies showed predominant PNS activity when putting the face in water, during immersion and when ambient pressure increased. [ABSTRACT FROM AUTHOR]

Purpose: To examine the effect of freediving depth on risk for hypoxic blackout by recording arterial oxygen saturation (SpO2) and heart rate (HR) during deep and shallow dives in the sea. Methods: Fourteen competitive freedivers conducted open-water training dives wearing a water-/pressure proof pulse oximeter continuously recording HR and SpO2. Dives were divided into deep (> 35 m) and shallow (10–25 m) post-hoc and data from one deep and one shallow dive from 10 divers were compared. Results: Mean ± SD depth was 53 ± 14 m for deep and 17 ± 4 m for shallow dives. Respective dive durations (120 ± 18 s and 116 ± 43 s) did not differ. Deep dives resulted in lower minimum SpO2 (58 ± 17%) compared with shallow dives (74 ± 17%; P = 0.029). Overall diving HR was 7 bpm higher in deep dives (P = 0.002) although minimum HR was similar in both types of dives (39 bpm). Three divers desaturated early at depth, of which two exhibited severe hypoxia (SpO2 ≤ 65%) upon resurfacing. Additionally, four divers developed severe hypoxia after dives. Conclusions: Despite similar dive durations, oxygen desaturation was greater during deep dives, confirming increased risk of hypoxic blackout with increased depth. In addition to the rapid drop in alveolar pressure and oxygen uptake during ascent, several other risk factors associated with deep freediving were identified, including higher swimming effort and oxygen consumption, a compromised diving response, an autonomic conflict possibly causing arrhythmias, and compromised oxygen uptake at depth by lung compression possibly leading to atelectasis or pulmonary edema in some individuals. Individuals with elevated risk could likely be identified using wearable technology. [ABSTRACT FROM AUTHOR]

Deep breathing exercises are the second most used complementary health approach in the United States. Two heart rate variability (HRV) parameters, the root mean square of successive differences (RMSSD) and the respiratory sinus arrhythmia (RSA), are used to assess parasympathetic reactivity to deep breathing, but they are often not in agreement. Our purpose was to determine the cause of the disagreement. We investigated HRV parameters in 38 subjects during baseline, deep breathing, and recovery. Here we show that RMSSD as a measure of parasympathetic reactivity is unreliable; it does not reflect the increase in HRV during deep breathing as determined by RSA. We observed a decrease in RMSSD values despite a marked increase in HRV as determined by RSA and the standard deviation of normal heartbeat interval (SDNN) in healthy subjects and patients with functional bowel disorders. We show that RSA captures all aspects of HRV, whereas successive differences in heart rate intervals are only a small part of HRV, with decreasing variability during deep breathing in most subjects. We present a new measure of calculating RSA during deep breathing that may become an essential tool for researchers and clinicians. We also provide a unique visualization of the increased heart rate variability during deep breathing. Hence, RMSSD cannot be used to assess parasympathetic reactivity during deep breathing; using RSA is recommended. The use of RMSSD in previous influential studies may have led to erroneous conclusions about parasympathetic reactivity during deep breathing. Its continued use may undervalue the effects of the autonomic nervous system in slow deep breathing. [ABSTRACT FROM AUTHOR]

Hyperoxia has been described to induce bradycardia by direct stimulation of the parasympathetic nervous system. Also, hyperoxia has been found to increase blood pressure by an elevation of vascular resistance. However, the latter effect itself would induce bradycardia by baroreceptor stimulation. This single-arm monocentric retrospective study aims to evaluate the correlation between these effects by investigating the relation between oxygen (O2) administration and heart rate over time. Data were collected from 23 patients without cardiovascular problems undergoing hyperbaric oxygen therapy (2.4 bar) retrospectively. During single oxygen bouts, transcutaneously measured partial pressure of O2 was increased. During this surge of oxygen pressure, the arterial blood pressure was increased while the heart rate was decreased. Respiration rate was maintained independently from breathing 100% O2 or air. During single oxygen bouts, the half-life of transcutaneously measured partial pressure of O2 was 5.4 ± 2.1 mmHg/s, and the half-life of heart rate was 0.45 ± 0.19 beats/min. It has been shown that hyperbaric oxygen therapy increases the transcutaneously measured partial pressure of O2. This increase was rather fast, followed by a rather slow decrease in HR. This finding does not support direct vagal activation. Heart rate is not decreased due to a direct vagal activation during hyperbaric oxygen therapy. Our single-arm, retrospective study has additionally confirmed that oxidative stress injures the endothelium, and the reduced endothelial-derived vasodilators cause vasoconstriction. As a consequence, blood pressure increases, and heart rate is then further decreased via the baroreceptor reflex. [ABSTRACT FROM AUTHOR]

Objective. Autonomic nervous system function and thereby bodily stress and recovery reactions may be assessed by wearable devices measuring heart rate (HR) and its variability (HRV). So far, the validity of HRV-based stress assessments has been mainly studied in healthy populations. In this study, we determined how psychosocial stress affects physiological and psychological stress responses in both young (18â€"30 years) and middle-aged (45â€"64 years) healthy individuals as well as in patients with arterial hypertension and/or either prior evidence of prediabetes or type 2 diabetes. We also studied how an HRV-based stress index (Relax-Stress Intensity, RSI) relates to perceived stress (PS) and cortisol (CRT) responses during psychosocial stress. Approach. A total of 197 participants were divided into three groups: (1) healthy young (HY, N  = 63), (2) healthy middle-aged (HM, N  = 61) and (3) patients with cardiometabolic risk factors (Pts, N  = 73, 32â€"65 years). The participants underwent a group version of Trier Social Stress Test (TSST-G). HR, HRV (quantified as root mean square of successive differences of Râ€"R intervals, RMSSD), RSI, PS, and salivary CRT were measured regularly during TSST-G and a subsequent recovery period. Main results. All groups showed significant stress reactions during TSST-G as indicated by significant responses of HR, RMSSD, RSI, PS, and salivary CRT. Between-group differences were also observed in all measures. Correlation and regression analyses implied RSI being the strongest predictor of CRT response, while HR was more closely associated with PS. Significance. The HRV-based stress index mirrors responses of CRT, which is an independent marker for physiological stress, around TSST-G. Thus, the HRV-based stress index may be used to quantify physiological responses to psychosocial stress across various health and age groups. [ABSTRACT FROM AUTHOR]

Purpose: Deep diving using mixed gas with closed-circuit rebreathers (CCRs) is increasingly common. However, data regarding the effects of these dives are still scarce. This preliminary field study aimed at evaluating the acute effects of deep (90–120 msw) mixed-gas CCR bounce dives on lung function in relation with other physiological parameters. Methods: Seven divers performed a total of sixteen open-sea CCR dives breathing gas mixture of helium, nitrogen and oxygen (trimix) within four days at 2 depths (90 and 120 msw). Spirometric parameters, SpO2, body mass, hematocrit, short term heart rate variability (HRV) and critical flicker fusion frequency (CFFF) were measured at rest 60 min before the dive and 120 min after surfacing. Results: The median [1st–3rd quartile] of the forced vital capacity was lower (84% [76–93] vs 91% [74–107] of predicted values; p = 0.029), whereas FEV1/FVC was higher (98% [95–99] vs 95% [89–99]; p = 0.019) after than before the dives. The other spirometry values and SpO2 were unchanged. Body mass decreased from 73.5 kg (72.0–89.6) before the dives to 70.0 kg (69.2–85.8) after surfacing (p = 0.001), with no change of hematocrit or CFFT. HRV was increased as indicated by the higher SDNN, RMSSD and pNN50 after than before dives. Conclusion: The present observation represents the first original data regarding the effects of deep repeated CCR dives. The body mass loss and decrease of FVC after bounce dives at depth of about 100 msw may possibly impose an important physiological stress for the divers. [ABSTRACT FROM AUTHOR]

Introduction: Scuba diving likely has an impact on the autonomic nervous system (ANS). In the course of conducting trials of underwater ECG recording for measurement of heart rate variability, there was an unexpected stressful event; one participant’s regulator iced and began to free-flow. Methods: A custom-made, water- and pressure-tight aluminum housing was used to protect a portable Holter monitor. ECGs were recorded in three experienced divers who witnessed an unplanned moderately stressful incident during diving. The ECG signals were analysed for measures of heart rate variability (HRV). Results: Analysis for different short-term HRV measures provided consistent results if periods of interest were appropriately time-aligned. There was improvement in sympatho-vagal balance. One diver unexpectedly exhibited an increase in both sympathetic and vagal activity shortly after the incident. Conclusions: A conventional open-water dive affected the ANS of experienced recreational divers as measured by HRV which provides a global evaluation of the ANS and alterations in its two branches. The heart rate variability data gathered from several participating divers around the time of this event illustrate the potential utility of this variable in quantifying stress during diving. HRV data may be useful in addressing relevant diving related questions such as effects of cold, exercise or different breathing gases on ANS function. [ABSTRACT FROM AUTHOR]

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Background: Depression is associated with reduced heart rate variability (HRV) in healthy and cardiac samples, which may be accounted for by physical fitness. In a small sample of cardiac patients, activity and fitness levels attenuated the relationship between HRV and depression. In the current study of heart failure (HF) patients, we hypothesized that depressive symptoms and HRV would be inversely related and physical fitness would attenuate this association.Purpose: To determine if previous associations among depressive symptoms, physical fitness, and HRV would replicate in a sample of HF patients.Methods: The sample consisted of HF patients (N = 125) aged 68.55 ± 8.92 years, 68.8% male, and 83.2% Caucasian. The study was cross-sectional and a secondary analysis of a nonrandomized clinical trial (Trial Identifier: NCT00871897). Depressive symptoms were evaluated using the Beck Depression Inventory (BDI)-II, fitness with the 2 min step test (2MST), and HRV during a 10 min resting laboratory psychophysiology protocol. The dependent variable in hierarchical linear regressions was the root mean square of successive differences.Results: Controlling for sex, age, β-blocker use, hypertension, and diabetes, higher BDI-II scores significantly predicted lower HRV, β = -.29, t(92) = -2.79, p < .01. Adding 2MST did not attenuate the relationship in a follow-up regression.Conclusion: Depressive symptoms were associated with lower HRV in HF patients, independent of physical fitness. Given the prevalence of depression and suppressed HRV common among HF patients, interventions addressing depressive symptoms and other predictors of poor outcomes may be warranted. [ABSTRACT FROM AUTHOR]

Introduction: The influence of acute exercise on sensory sensitivity (SS) differs according to the type and duration of exercise performed. In the present study, we assessed changes on SS soon after a maximal dynamic apnoea. Methods: Thirty-nine experienced male breath-hold divers were recruited. Critical flicker fusion frequency (CFFF) thresholds were used to measure SS. Thresholds were determined before and after a maximal dynamic apnoea. Immediately after surfacing, heart rate and oxygen saturation (SpO2) were recorded for two minutes. Results: After maximal dynamic apnoea, SpO2 was significantly decreased (from mean 97.3% pre-dive to mean 63.1% postdive; P < 0.0001; η² P = 0.86), but this acute hypoxaemia did not trigger changes in SS (post-dive value 102% of baseline; P = 0.22; η² P = 0.03). Pearson correlation analysis revealed a moderate association between SS with swimming speed (r = 0.423) and apnoea time (r = -0.404). Conclusions: A maximal dynamic apnoea did not produce changes in central nervous system fatigue or cortical arousal. We found no relationship between the hypoxaemia level reached after a maximal apnoea and changes in the CFFF thresholds. This study suggests that the time of exposure to hypoxia during a maximal voluntary apnoea is not enough to produce changes in SS. [ABSTRACT FROM AUTHOR]

The descent is a critical part of a dive, both physically and mentally. Pulmonary ventilation, expressed as respiratory minute volume (RMV) and heart rate (HR) were recorded during fast and slow descents to 35 meters (m) in open water while breathing compressed air, and during swimming horizontally at moderate velocity at an 11-m depth. Values of both types of descents were compared with reference values recorded at 11 m, the "plateau" phase, halfway through the 35-m dives. It is hypothesized that the "slow-descent" and "plateau-phase" values will be less than 'fast-descent values. Depth, cylinder pressure, water temperature and HR were recorded with a dive computer yielding time-averaged means (mRMV and mHR) for the descent and for plateau. Of the 18 divers included, 16 performed the fast descents and 11 made the slow descents. The fast descents (23 m⋅min-1 vertically), performed with 0-8 fin kicks, yielded mRMVDescent=28 ambient L (aL)⋅min-1, which is 82% higher (P<0.001) than mRMVPlateau of 15 aL⋅min-1. Further, mHRDescent was 121 beats⋅min-1 23% higher (P<0.001), than mHRPlateau of 100 bpm. Slow descents (2.4 m⋅min-1 vertically) yielded 17 aL⋅min-1 with mHR=101 beats⋅min-1, values only slightly higher than at Plateau. The 11-m dive (swimming horizontally) yielded 24 m⋅min-1 with 32 fin kicks⋅min-1, mRMV=35 aL⋅min-1 and mHR=115 beats⋅min-1. Fast descents cause a higher RMV and HR that cannot be explained by physiology alone. Presumably mental stress is a main contributor. For dives deeper than 20 m, a descent velocity of 10 m⋅min-1 is recommended to reduce cardiac stress, in particular for older divers. [ABSTRACT FROM AUTHOR]

Aim: Aquatic exercise might improve endothelial function due to hydrostatic pressure increasing blood flow and causing shear stress to the endothelium. However, the acute effect of aerobic exercise in water on endothelial function is unclear. The present study compares the acute effect of aerobic exercise at moderate intensity in water and on land on endothelial function. Methods: Nine healthy young men walked on a treadmill for 30 min while immersed in water up to the xiphoid at 30.0 ± 0.2°C and on land at an intensity equivalent to 60% heart rate reserve in a crossover trial. Brachial artery flow-mediated dilation (FMD) was measured at baseline and at 30 and 60 min after exercise. Autonomic nervous activity was compared among conditions at the heart rate variability (HRV) during exercise. Results: FMD significantly decreased at 30 min after exercise on land trial (p < 0.05), but did not change after the aquatic trial. However, FMD was significantly higher after aquatic trial than land trial (p < 0.05) at 30 and 60 min after exercise, whereas heart rate, blood pressure, and HRV did not significantly differ between them. Conclusion: These findings demonstrate that aerobic exercise in water suppressed the decrease in FMD compared with that on land, regardless of autonomic nervous activity. [ABSTRACT FROM AUTHOR]

This paper presents a unified approach based on the recurrence quantification analysis (RQA) and approximate entropy (ApEn) for the classification of heart rate variability (HRV). In this paper, the optimum tolerance threshold (ropt) corresponding to ApEnmax has been used for RQA calculation. The experimental data length (N) of RR interval series (RRi) is optimized by taking ropt as key parameter. ropt is found to be lying within the recommended range of 0.1 to 0.25 times the standard deviation of the RRi, when N ≥ 300. Consequently, RQA is applied to the age stratified RRi and indices such as percentage recurrence (%REC), percentage laminarity (%LAM), and percentage determinism (%DET) are calculated along with ApEnmax, [Formula: see text], [Formula: see text], and an index namely the radius differential (RD). Certain standard HRV statistical indices such as mean RR, standard deviation of RR (or NN) interval (SDNN), and the square root of the mean squared differences of successive RR intervals (RMSSD) (Eur Hear J 17:354-381, 1996) are also found for comparison. It is observed that (i) RD can discriminate between the elderly and young subjects with a value of 0.1151 ± 0.0236 (mean ± SD) and 0.0533 ± 0.0133 (mean ± SD) respectively for the elderly and young subjects and is found to be statistically significant with p < 0.05. (ii) Similar significant discrimination was obtained using [Formula: see text] with a value of 0.1827 ± 0.0382 (mean ± SD) and 0.2248 ± 0.0320 (mean ± SD) (iii) other significant indices were found to be %REC, %DET, %LAM, SDNN, and RMSSD; however, ApEnmax was found to be insignificant with p > 0.05. The above features of RRi time series were tested for classification using support vector machine (SVM) and multilayer perceptron neural network (MLPNN). Higher classification accuracy was achieved using SVM with a maximum value of 99.71%. Graphical abstract. [ABSTRACT FROM AUTHOR]

The article offers information on study of Glossopharyngeal insufflation (GI) and papillary muscles using cardiovascular magnetic resonance (CMR). It mentions GI develop due to greatly reduced end‐systolic volumes, relative to intrathoracic hypovolemial; Cardiovascular consequences of GI like reduced coronary blood flow; and hypovolemic conditions can occur after intense GI (lung packing), as practiced shortly before breathhold deep diving.

Light is a common ambient medium to express additional information in a peripheral and calm way, but it is also an environmental stimulant to create atmosphere, evoke moods, and provide immersive experiences. Through the design of the DeLight system, we aim to establish a biofeedback-driven lighting environment that informs users about their stress level for intervention and assists them in biofeedback relaxation training. In this study, DeLight is interfaced with a heart rate variability biofeedback system with two modes for different purposes: stress intervention and relaxation assistance. We evaluated the prototype of DeLight in two user studies. The results of the first study show that DeLight has the potential for stress intervention; the HRV biofeedback through the changes of ambient light could improve a user’s awareness of stress and trigger behavioral conditioning, such as deep breathing. The results of the second study confirm that DeLight has potential as a new biofeedback interface for relaxation assistance; biofeedback through an immersive lighting environment can support physiological regulation as effectively as graphic biofeedback; it offers enhanced relaxation effects regarding both subjective experience and physiological arousal. These findings suggest that the biofeedback-driven ambient light can perform as persuasive technology in the domain of health self-management. The combination of decorative and informative aspects enables the lighting interface to offer the users a comfortable and relaxing condition for biofeedback-assisted relaxation training. [ABSTRACT FROM AUTHOR]

Summary: Background: Water immersion and aquatic exercise can be an important therapeutic tool in patients suffering from heart disease (HD). However, the effects of water immersion on heart rate variability (HRV) in HD participants remain unknown. Methods: Twenty‐eight volunteers in sinus rhythm within the same age range took part in this study: 18 HD and ten healthy controls (HC). Heart rhythm was collected with a heart rate monitor (sampling rate 1000 Hz) for periods of 10 min at rest in the supine position on land, standing on land (STL) and standing in water (STW) to the xiphoid process. Results: Heart disease participants had the same response as HC participants to the three experimental conditions (no significant between‐group differences in all HRV variables). STW (immersion) caused in both groups to increase HRV when compared to supine and STL. Conclusion: Heart disease participants demonstrate similar beneficial adaptations as HC participants to the effects of immersion, reinforcing the concept that immersion can be a valuable aquatic cardiac rehabilitation tool to acutely increase HRV. Approaches that improve HRV in both healthy and cardiac patients may have a positive impact on the reduction of morbidity and mortality. [ABSTRACT FROM AUTHOR]

Purpose: Through time- and frequency-domain analysis, we compared the effects of acute hypobaric hypoxia on the changes in heart rate variability (HRV) following night sleeping and morning awakening in individuals with and without acute mountain sickness (AMS).Method: Thirty-nine nonacclimatised healthy individuals were transported by bus from sea level to 3150 m within 3 h. Short-term HRV was measured two times a day-before sleeping (BS) and after awakening (AA)- at 3 days before ascent (T0), two consecutive nights at 3150 m (T1 and T2), and 2 days after descent (T3). AMS was diagnosed using the self-reported Lake Louise score questionnaire.Result: AMS developed in 19 of 39 participants (48.7%). At sea level, individuals had higher HRV at AA than at BS, and the trend of increased HRV at AA remained unchanged at high altitude, irrespective of AMS. At T1 BS, low-frequency power in normalised unit was significantly lower in participants with AMS than in those without AMS. Compared with those at T1 BS, the square root of the mean squared differences of successive normal-normal (NN) intervals, the number of interval differences of successive NN intervals more than 50 ms (NN50), and the proportion derived by dividing NN50 by the total number of NN intervals at T1 AA significantly increased in participants without AMS but nonsignificantly decreased in those with AMS.Conclusion: After rapid ascent, individuals with AMS did not demonstrate sympathetic hyperactivity but did exhibit withdrawal of cardiac vagal modulation in the morning following the first night's sleep. [ABSTRACT FROM AUTHOR]

The article discusses a study related to assessment and comparison of heart rate variability (HRV) status of women with higher body mass index (BMI) and women with normal BMI. It mentions results showing predominance of sympathetic activity in young overweight and obese females. It also mentions a reduced HRV in healthy young females who are overweight and obese.

Traumatic experiences have severe impact on the autonomous nervous system. Heart rate variability (HRV) is a reliable psychophysiological marker for the autonomous nervous system functioning. Reduced vagally mediated HRV has been found in patients with post-traumatic stress disorder (PTSD) and, in some studies, in patients with borderline personality disorder (BPD). In this study, we compared HRV parameters of patients with PTSD, current BPD, and BPD in remission with healthy volunteers in a 5 min resting-state electrocardiogram recording. 91 unmedicated female participants took part in the study (18 with PTSD, 27 with the current BPD, 23 with BPD in remission, and 23 healthy volunteers). We found significant group differences in both time-domain and frequency-domain (total power, low-frequency and high-frequency power) HRV parameters. Root mean square of the successive differences (RMSSD) was lowest in patients with PTSD (M = 48.6 ms, SD = 23.5 ms) followed by patients with BPD in remission (M = 57.7 ms, SD = 31.5 ms) and patients with the current BPD (M = 71.1 ms, SD = 44.5 ms), while the highest RMSSD was found in healthy volunteers (M = 84.1 ms, SD = 41.7 ms). Variance of HRV was higher in patients with BPD than in patients with PTSD. In addition, RMSSD was significantly negatively correlated with self-reported early life maltreatment assessed with the Childhood Trauma Questionnaire. Our findings point out a complex interaction between traumatic experiences, the functioning of the autonomic nervous system, and psychopathology. Alterations in HRV might be related to early life maltreatment or associated psychological factors rather than diagnostic entities. [ABSTRACT FROM AUTHOR]

Purpose: Although it has been demonstrated that the exponential decay model fits the heart rate (HR) kinetics in short static breath holding (BH), this model might be inaccurate when BH is maintained for several minutes. The aim of this study was to build a new meaningful model to quantify HR kinetics during prolonged static BH. Methods: Nonlinear regression analysis was used to build a model able to quantify the beat-to-beat HR reduction kinetics observed in prolonged static BH performed both in air and in immersed condition by 11 trained breath-hold divers. Dynamic changes in cardiac autonomic regulation through heart rate variability indices [root mean square of successive difference of R-R intervals (RMSSD); short-term fractal scaling exponent: (DFAα1)] and peripheral oxygen saturation (SpO) were also analyzed to strengthen the model. Results: The tri-phasic model showed a sharp exponential drop in HR immediately followed by a slight linear rise up until a breaking point preceding a linear drop in HR. The breaking points had similar level of SpO whether in air or in immersed condition (95.1 ± 2.1 vs. 95.2 ± 3.0 %, respectively; P = 0.49), and the subsequent linear drop in HR was concomitant with a shift in cardiac autonomic regulation in air (RMSSD: +109.0 ± 47.8 %; P < 0.001; DFAα1: −18.0 ± 17.4 %; P < 0.05) and in immersion (RMSSD: +112.6 ± 55.8 %; P < 0.001; DFAα1: −26.0 ± 12 %; P < 0.001). Conclusion: In addition to accurately fitting the HR kinetics, the most striking finding is an 'oxygen-conserving breaking point' highlighted by the model, which might be interpreted as unique adaptive feature against hypoxic damages in the human diving bradycardia. [ABSTRACT FROM AUTHOR]

Purpose: Voluntary breath-holding (BH) elicits several hemodynamic changes, but little is known about maximal static immersed-body BH. We hypothesized that the diving reflex would be strengthened with body immersion and would spare more oxygen than maximal dry static BH, resulting in a longer BH duration. Methods: Eleven trained breath-hold divers (BHDs) performed a maximal dry-body BH and a maximal immersed-body BH. Cardiac output (CO), stroke volume (SV), heart rate (HR), left ventricular end-diastolic volume (LVEDV), contractility index (CTI), and ventricular ejection time (VET) were continuously recorded by bio-impedancemetry (PhysioFlow PF-05). Arterial oxygen saturation (SaO) was assessed with a finger probe oximeter. Results: In both conditions, BHDs presented a bi-phasic kinetic for CO and a tri-phasic kinetic for SV and HR. In the first phase of immersed-body BH and dry-body BH, results (mean ± SD) expressed as percentage changes from starting values showed decreased CO (55.9 ± 10.4 vs. 39.3 ± 16.8 %, respectively; p < 0.01 between conditions), due to drops in both SV (24.9 ± 16.2 vs. 9.0 ± 8.5 %, respectively; p < 0.05 between conditions) and HR (39.7 ± 16.7 vs. 33.6 ± 17.0 %, respectively; p < 0.01 between conditions). The second phase was marked by an overall stabilization of hemodynamic variables. In the third one, CO kept stabilizing due to increased SV (17.0 ± 20.2 vs. 10.9 ± 13.8 %, respectively; p < 0.05 between conditions) associated with a second HR drop (14.0 ± 10.0 vs. 12.7 ± 8.9 %, respectively; p < 0.01 between conditions). Conclusion: This study highlights similar time-course patterns for cardiodynamic variables during dry-body and immersed-body BH, although the phenomenon was more pronounced in the latter condition. [ABSTRACT FROM AUTHOR]

Methods to predict onset of cardiopulmonary (CP) decompression sickness (DCS) would be of great benefit to clinicians caring for stricken divers. Principal dynamic mode (PDM) analysis of the electrocardiogram has been shown to provide accurate separation of the sympathetic and parasympathetic tone dynamics. Nine swine (Sus scrofa) underwent a 15-h saturation dive at 184 kPa (60 ft. of saltwater) in a hyperbaric chamber followed by dropout decompression, whereas six swine, used as a control, underwent a 15-h saturation dive at 15 kPa (5 ft. of saltwater). Noninvasive electrocardiograms were recorded throughout the experiment and autonomic nervous system dynamics were evaluated by heart rate series analysis using power spectral density (PSD) and PDM methods. We observed a significant increase in the sympathetic and parasympathetic tones using the PDM method on average 20 min before DCS onset following a sudden induction of decompression. Parasympathetic activities remained elevated, but the sympathetic modulation was significantly reduced at onset of cutis and CP DCS signs, as reported by a trained observer. Similar nonsignificant observations occurred during PSD analysis. PDM observations contrast with previous work showing that neurological DCS resulted in a >50% reduction in both sympathetic and parasympathetic tone. Therefore, tracking dynamics of the parasympathetic tones via the PDM method may allow discrimination between CP DCS and neurological DCS, and this significant increase in parasympathetic tone has potential use as a marker for early diagnosis of CP DCS. [ABSTRACT FROM AUTHOR]

Cardiac changes induced by repeated breath-hold diving were investigated after a fish-catching diving competition. Eleven healthy subjects carried out repeated breath-hold dives at a mean maximal depth of 20 ± 2.7 msw (66 ± 9 fsw) during 5 h. One hour after the competition, the body mass loss was −1.7 ± 0.5 kg. Most of the breath-hold divers suffered from cold and although the core temperature remained normal, a decrease in cutaneous temperature was recorded in the extremities. Systolic blood pressure was reduced in both upper and lower limbs. Heart rate was unchanged, but left ventricular (LV) stroke volume was reduced leading to a decrease in cardiac output (−20%). Left atrial and LV diameters were significantly decreased. LV filling was assessed on a trans-mitral profile. An increase in the contribution of the atrial contraction to LV filling was observed. Right cavity diameters were increased. The cardiac autonomic alterations were in favor of sympathetic hyperactivity. After a fish-catching diving competition in cold water, alterations suggesting dehydration, contraction in plasma volume and sympathetic hyperactivity were observed. Furthermore, enlargements of right cavities were in favor of right ventricular strains. Repeated apnea and swimming in cold water may account for these alterations. [ABSTRACT FROM AUTHOR]

With this study we wanted to test the hypothesis that individual like and dislike as occurring in relation to brand attitude can be objectively assessed. First, individuals rated common brands with respect to subjective preference. Then, they volunteered in an experiment during which their most liked and disliked brand names were visually presented while three different objective measures were taken. Participant's eye blinks as responses to acoustic startle probes were registered with electromyography (EMG) (i) and their skin conductance (ii) and their heart rate (iii) were recorded. We found significantly reduced eye blink amplitudes related to liked brand names compared to disliked brand names. This finding suggests that visual perception of liked brand names elicits higher degrees of pleasantness, more positive emotion and approach-oriented motivation than visual perception of disliked brand names. Also, skin conductance and heart rate were both reduced in case of liked versus disliked brand names. We conclude that all our physiological measures highlight emotion-related differences depending on the like and dislike toward individual brands. We suggest that objective measures should be used more frequently to quantify emotion-related aspects of brand attitude. In particular, there might be potential interest to introduce startle reflex modulation to measure emotion-related impact during product development, product design and various further fields relevant to marketing. Our findings are discussed in relation to the idea that self reported measures are most often cognitively polluted. [ABSTRACT FROM AUTHOR]

In this meta-analysis of diving bradycardia in humans, we sought to quantify any heart rate (HR) reduction using a relatively simple mathematical function. Using the terms 'diving reflex,''diving bradycardia,''diving response,''diving plus heart rate,' databases were searched. Data from the studies were fitted using HR= c+ aexp(−( t− t)/τ), where c is the final HR, a is the HR decrease, τ is the time constant of HR decay, and t is the time delay. Of 890 studies, 220 were given closer scrutiny. Only eight of these provided data obtained under comparable conditions. Apneic facial immersion decreased HR with τ=10.4 s and in air alone it was less pronounced and slower (τ=16.2 s). The exponential function fitted the time course of HR decrease closely ( r>0.93). The fit was less adequate for apneic-exercising volunteers. During apnea both with and without face immersion, HR decreases along a monoexponential function with a characteristic time constant. HR decrease during exercise with and without face immersion could not readily be described with a simple function: the parasympathetic reaction was partially offset by some sympathetic activity. Thus, we succeeded in quantifying the early time course of diving bradycardia. It is concluded that the diving reflex is useful to diagnose the integrity of efferent cardiovascular autonomic pathways. [ABSTRACT FROM AUTHOR]

Ivabradine represents a novel heart-rate-lowering agent that acts on the sino-atrial node supposedly by selectively inhibiting the 'funny' current (If current). In clinical studies, it was reported that ivabradine effectively reduced resting heart rate and was well tolerated. The aim of this study was to evaluate potential effects of ivabradine on cardiac contractility. Contractile effects of ivabradine were studied in isolated electrically driven atrial preparations from patients undergoing cardiac bypass surgery and for comparison in isolated spontaneously beating right atria and electrically driven left atria from mice. In human trabeculae, a concentration-dependent negative inotropic effect was noted in 7 from 10 patients. However, in 3 patients from 10, a pronounced positive inotropic effect of ivabradine was noted. As expected, in spontaneously beating mouse right atria ivabradine exerted a concentration-dependent negative chronotropic effect. Unexpectedly, contractile effects in mouse and man seem to disagree. In mouse left atria, ivabradine and cilobradine, another hyperpolarization-activated cyclic-nucleotide-gated blocker, always exerted a pronounced positive inotropic effect. These positive inotropic effects were converted to negative inotropic effects in the additional presence of the L-type Ca2+ channel blocker verapamil. The present study demonstrates that ivabradine at high concentrations can affect the force of contraction in atrial preparations from the human heart. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

It was already established that exposure to hyperbaric conditions induces vagal-depended bradycardia but field study on autonomic nervous system (ANS) activity during self-contained underwater breathing apparatus (SCUBA) diving is lacking. The aim of the present study was to evaluate ANS modifications during real recreational SCUBA diving using heart rate variability analysis (timedomain, frequency-domain and Poincaré plot) in 10 experienced and volunteers recreational divers. Mean RR, root mean square of successive differences of interval (rMSSD), high frequency of spectral analysis and standard deviation 1 of Poincaré Plot increased (P < 0.05) during dive. Low frequency/high frequency ratio decreased during dive (P < 0.05) but increased after (P < 0.05). Recreational SCUBA diving induced a rise in vagal activity and a decrease in cardiac sympathetic activity. Conversely, sympathetic activity increases (P < 0.05) during the recovery. [ABSTRACT FROM AUTHOR]

To compare the changes in heart rate variability (HRV) and blood pressure (BP) between standard head-up tilt test (HUT) and nitroglycerin administration. Eighteen healthy men and women aged 23–58 years participated. HRV was assessed using standard methods at rest and during both tests. Heart rate and BP data were collected during a standard HUT (maximal tilt = 70° for 10 minutes) and following administration of 0.4 mg of nitroglycerin during supine rest. Test order was randomized. Repeated measure ANOVA was used to determine if changes in HRV and BP were significantly different between treatments. Paired t tests were used to examine the change from baseline to treatment for each variable. As compared to HUT, the change in diastolic blood pressure and HRV measures was significantly ( P < 0.05) less after nitroglycerin administration. However, no significant differences ( P > 0.05) in HRV variables were found between nitroglycerin administration and HUT during the 5th and 6th minutes of each test. Nitroglycerin administration and HUT caused significantly different changes in HRV over a ten-minute average. However nitroglycerin produced its maximal effect on HRV during the 5th and 6th minutes, which was similar to the effect caused by HUT at the same time. When using nitroglycerin administration to assess changes in HRV indices, the fifth and sixth minutes of testing will provide information similar to that of a HUT protocol. [ABSTRACT FROM AUTHOR]

Adaptation of action potential duration (APD) to pacing cycle length (CL) has been previously characterized in isolated cardiomyocytes for sudden changes in constant CL and for pre-/postmature stimuli following constant pacing trains. However, random fluctuations characterize both physiological sinus rhythm (up to 10% of mean CL) and intrinsic beat-to-beat APD at constant pacing rate. We analysed the beat-to-beat sensitivity of each APD to the preceding CL during constant–sudden, random or linearly changing pacing trains in single patch clamped rat left ventricular myocytes, in the absence of the autonomic and electrotonic effects that modulate rate dependency in the intact heart. Beat-to-beat variability of APD at −60 mV (APD−60 mV), quantified ass.d. over 10-beat sequences, increased with corresponding mean APD. When measured as coefficient of variability (CV), APD−60 mV variability was inversely proportional to pacing frequency (from 1.2% at 5 Hz to 3.2% at 0.2 Hz). It was increased, at a basic CL (BCL) of 250 ms, by 55% by the L-type calcium current ( ICaL) blocker nifedipine, and decreased by 23% by the transient-outward potassium current ( Ito) blocker 4-aminopyridine. Variability of APD at BCL of 250 ms prevented the detection of random changes of CL smaller than ∼5%. Ten per cent random changes in CL were detected as a 40% increase in CV of APD and tended to correlate with it ( r= 0.43). Block of ICaL depressed this correlation ( r= 0.23), whereas block of Ito significantly increased it ( r= 0.67); this was similar with linearly changing CL ramps (ranging ±10% and ±20% of 250 ms). We conclude that beat-to-beat APD variability, a major determinant of the propensity for development of arrhythmia in the heart, is present in isolated myocytes, where it is dependent on mean APD and pacing rate. Action potential duration shows a beat-to-beat positive correlation with preceding randomly/linearly changing CL, which can be pharmacologically modulated. [ABSTRACT FROM AUTHOR]

Mitral annular (MA) excursion during diastole encompasses a volume that is part of total left ventricular (LV) filling volume (LVFV). Altered excursion or area variation of the MA due to changes in preload or inotropic state could affect LV filling. We hypothesized that changes in LV preload and inotropic state would not alter the contribution of MA dynamics to LVFV. Six sheep underwent marker implantation in the LV wall and around the MA. After 7-10 days, biplane fluoroscopy was used to obtain three-dimensional marker dynamics from sedated, closed-chest animals during control conditions, inotropic augmentation with calcium (Ca), preload reduction with nitroprusside (N), and vena caval occlusion (VCO). The contribution of MA dynamics to total LVFV was assessed using volume estimates based on multiple tetrahedra defined by the three-dimensional marker positions. Neither the absolute nor the relative contribution of MA dynamics to LVFV changed with Ca or N, although MA area decreased (Ca, P < 0.01; and N, P < 0.05) and excursion increased (Ca, P < 0.01). During VCO, the absolute contribution of MA dynamics to LVFV decreased (P < 0.001), based on a reduction in both area (P < 0.001) and excursion (P < 0.01), but the relative contribution to LVFV increased from 18 ± 4 to 45 ± 13% (P < 0.001). Thus MA dynamics contribute substantially to LV diastolic filling. Although MA excursion and mean area change with moderate preload reduction and inotropic augmentation, the contribution of MA dynamics to total LVFV is constant with sizeable magnitude. With marked preload reduction (VCO), the contribution of MA dynamics to LVFV becomes even more important. [ABSTRACT FROM AUTHOR]

Stress ulcer is clinically prevalent, but the underlying mechanisms are not well understood. This study aimed to investigate the role of sympathovagal imbalance in the development of water immersion restraint stress (WRS)-induced gastric mucosal lesion. Wistar rats were subjected to either restraint stress (RS) (n = 7) or WRS (n = 7) for 5 h. Linear parameters of heart rate variability and Poincaré plot were analyzed on the basis of the surface ECGs. Gastric mucosal lesion was evaluated by gross anatomy and histology. Mean R-R intervals significantly increased (P < 0.001) in a time-dependent manner in the WRS group but slightly decreased (P < 0.001) in the RS group. Root mean square of successive differences of R-R intervals and high-frequency norm (high-frequency power normalized by the total frequency power) were significantly higher in the WRS group than the RS group (P < 0.001). Low-frequency norm and low-to-high-frequency ratio increased significantly 1 h after stress and then declined to similar levels in both groups. The Poincaré plots of R-R intervals in the WRS group shifted right-upwardly and showed dispersed patterns compared with the RS group. Gastric mucosae showed serious hemorrhage, effusion, and structural collapse in the WRS group but remained normal in the RS group. Bilateral cervical vagotomy suppressed the increase of heart rate variability and prevented the gastric mucosal lesion induced by WRS. We conclude that parasympathetic overactivity is the predominant autonomic response to WRS and is most probably the leading mechanism of WRS-induced gastric mucosal lesion in rat. [ABSTRACT FROM AUTHOR]

Nitric oxide synthase (NOS) inhibitors elicit bradycardias independent of the endothelium (e-NOS) or increases in blood pressure. Therefore, this bradycardia could be mediated by other NOS isoforms, most likely that of the nervous system (n-NOS). If so, heart rate variability (HRV) as a measure of vagal activity should be an indicator of the activity of n-NOS in vagal neurons. To test this, we studied the dose-effect relations of L-NAME (0.3 – 50 mg·kg-1) on heart rate (HR), HRV and systemic vascular resistance (SVR) in seven awake dogs. HRV was analyzed in the time domain as standard deviation of the RR-intervals (SDNN) and in the frequency domain as power in the high (0.15 – 0.5 Hz) and low (0.04 – 0.15 Hz) frequency range. The effects of HR and SDNN reached their maxima at a dose of 3 mg·kg-1 and had their ED50 at 0.27 ± 0.03 mg·kg-1 and 0.43 ± 0.1 mg·kg-1, respectively, whereas SVR had its maximum at 10 mg·kg-1 and ED50 at 0.86 ± 0.11 mg·kg-1 (p < 0.05). HF-power (vagal activity) predominated compared to LF-power (mainly sympathetic activity) during baseline as well as after L-NAME. The effects on HR and HRV were absent after ganglionic blockade (hexamethonium), whereas the effects on SVR remained unchanged. Thus, NO exerts a powerful restraining activity on vagal neurons and plays a key role in the adjustment of heart rate in awake resting animals with prevailing vagal activity. [ABSTRACT FROM AUTHOR]